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McDougall Moments: Diarrhea

Updated November 5, 2023

In the video below, Dr. McDougall discusses the connection between fats and diarrhea and how to stop diarrhea.


McDougall Moments: Diarrhea

Video Summary

Some people feel “tied to their bathrooms.” They may even take their laptops in their bathrooms because they spend so much time there. They can’t have social events. They can’t have meetings. They know they’ll be overwhelmed by an urgency to move their bowels.

When I see someone like this I make a statement that shocks people. It shocks them so much that some would rather turn around and leave my program because they think I’m too radical for making such a statement:

Within 48 to 72 hours of changing their diet, specifically taking out oils and fats, their diarrhea will be gone.

Research from the National Library of Medicine showed a study with people who had terrible diarrhea problems due to damage to their ileum (last part of their small intestine). Researchers put them on a low-fat diet, and within two to three days, most people had two to four firm stools a day.

That’s right—in most cases, you can cure this “mystery” of chronic diarrhea through diet by getting rid of fats and oils. I’ve done this over and over again with patients who have high-fat diets and diarrhea.

Of course, you can get diarrhea by adding oil back into your diet. If you add lots of oil or just a little bit of oil back into your diet, you get something that I refer to as “McDougall’s Revenge,” where you’ll be in the bathroom immediately in terrible distress.

This occurs because fats and oils cause the liver to produce bile acids. Bile acids are extracted into the intestines and are supposed to be reabsorbed into the last part of the small intestine.

But, in a lot of people, they aren’t reabsorbed. Without reabsorption, bile acids pass into the colon, where they cause terrible irritation and diarrhea.

So, you stop the production of these bile acids by getting fat out of the diet because fat causes the production of bile acids in the liver. The second thing you do is add fiber, which will neutralize bile acids.

Those are the mechanisms, and the results are immediate.

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